Distributed energy resources (DERs) play an ever-increasing role in electrical power generation. Generally, a DER is a relatively low-power (relative to traditional utility-scale fossil fuel, hydroelectric and nuclear power plants) electricity-generating or—storage device that is connected to an electrical power system (EPS), for example, a utility power grid, to form a distributed energy system. Examples of DERs include diesel engine-generator sets, wind turbines, solar cells, fuel cells, backup batteries, and any combination of these. DERs are used for a number of reasons. For example, in some applications DERs are used to provide backup power when primary power from a utility grid is interrupted. In other applications DERs are used to reduce reliance on electrical power from a utility power grid. In still further applications, DERs are used to supplement power provided by conventional electrical power generators, such as fossil-fuel-fired and nuclear-fission driven power plants. DERs are becoming increasingly popular as more manufacturers are building DERs that generate electricity from renewable resources, such as wind and solar energy.
Regardless of the rise in popularity of DERs, an important requirement is that the connection of any given DER to an EPS does not significantly impact the quality of the electrical power on the EPS. Consequently, the proliferation of DERs into EPSs is greatly dependent on the quality of the interconnection equipment (which includes any software) used to connect DERs to EPSs. Interconnection equipment typically performs a number of functions as between a DER and the corresponding EPS, including, as necessary, voltage regulation, grounding integration, synchronization, power conversion, monitoring, isolation, voltage disturbance handling, frequency disturbance handling, harmonics handling, current disturbance handling, fault handling, etc. It can be challenging for interconnection equipment designers to design equipment that performs all of the needed functionality, while minimizing the complexity and cost of the equipment.